Jeremy Harris

I'd definitely want something like Heras, as public liability is pretty serious, and Heras (or similar) secure fencing is so widely used that it would be a pretty good legal defence argument is something did happen. The orange low level stuff is wholly inadequate, and only intended to be used for short duration hazard marking around temporary works, like roadworks. Our site insurers wanted security fencing that was at least 1.8m or 2m high, IIRC, I'll try and see if I kept the bumpf they sent out with the policy and quote it, if I haven't thrown it out.

I think there's some confusion here between "airtight" and "vapour tight". OSB is, to all intents and purpose, more than adequately airtight as far as a building air test is concerned. It won't let air through at a rate that would make a jot of difference to the house air tightness in practice. OSB is vapour permeable though, so will allow water vapour to move through it. As such, OSB is not suitable as a vapour control layer - for that you need to use one of the boards made specifically for vapour control, such as Spano DURÉLIS VapourBlock or SmartPly, or similar. Our build uses Spano DURÉLIS VapourBlock as the inner skin and OSB as the outer skin for this reason.

There are a couple of different companies that can make and supply filters for just about any MVHR at a lot lower price than the original manufacturers ones, but as @Temp says, you need to know what size and type the filters are. Generally MVHR filters need to either be changed (if they are non-washable) or cleaned/washed at least every 6 months. I've found that our intake filter gets badly fouled after 6 months and wouldn't want to leave it any longer before changing it. I've had custom replacement filters made for our Genvex MVHR by this company http://www.jasun-envirocare.com/for a great deal less than the cost of the real Genvex ones, and they look identical except for the label, but our unit has non-washable paper filters, so I don't have the option of being able to clean them, only try and vacuum them if they aren't too bad or replace them.

I fitted the display into a 2G blank faceplate with a rectangular hole milled in it and the rear face of the blanking plate milled off flat (there are moulded lumps and bumps that stop the display sitting flush). To finish it off I used a laser cut stainless bezel: http://www.picaxestore.com/index.php/en_gb/bzl020.html

Normally, yes, as PD rights for permanent structures is tied to their being a completed building that, in effect "owns" those PD rights. Temporary structures are different in that their rights aren't "owned" by any structure. You can have PD rights, for example, to erect a polytunnel-type aircraft hangar in a field, something that a lot of small aeroplane owners take advantage of. They are subject to a different set of rules regarding change of use for the land, the "28 day rule", which isn't relevant to the temporary building erected under PD rights, but does mean they can only use the land as an airfield for 28 days in any 12 month period. The classic way around this is for a group to get together and buy a field and divide it into separately owned strips. They can then spread their use around amongst the several differently owned strips and so get a whole years worth of flying out it, as long a no single strip is used for more than 28 days in any 12 months.

Our DNO is SSE. I had a site visit to look at relocating a pole, running some existing supply cables underground (they were right over where we needed to get diggers in and out) and relocate (free of charge) a big three phase cable running diagonally across the plot that had no easement or wayleave (the DNO didn't even know it was there...). This site visit was in February. The DNO and I agreed a price for the work, with our ground works chap doing the contestable element and the DNO doing the non-contestable element. I was required to pay the DNO in full in April, with a date set for the pole to moved, underground cables pulled through the ducts we were putting in to their spec, at the end of June. The DNO eventually got around to moving the cables and installing the new pole in August, having delayed us for weeks. Even then they didn't remove the old pole; that sat there for another year until I slipped a few pounds to a passing Openreach team who were using their Polecat to replace another pole up the road, and got them to pull SSEs old pole out of the ground and "donate" it to me.

The idea of an interior design course sounds more useful than going to the Grand Designs show, or some of the other shows, come to that. We were both fairly disappointed with most of the shows we went to, the one exception being the self build and renovation centre in Swindon ( https://www.nsbrc.co.uk/ ). We've been there probably four or five times now, and found it far and away the best of them.

Because I can't physically fit a post cooler and condensate drain in the space available between the MVHR and the fresh air distribution plenum. Ideally that's where I'd put it, but it wasn't something I'd thought about when installing the MVHR, and almost all the ducts running to that distribution plenum come up through the floor right next to it, so it can't now be easily re-positioned. The reason I decided to fit a heat exchanger in the intake is driven by another slight problem I want to fix. The external air intake is up under the eaves of the house and regularly gets clogged up with cobwebs, fluffy seeds, etc in summer. Also, the F7 intake filter on the MVHR gets very badly fouled by lots of coarse stuff, small flies that get through the intake grill etc. Luckily the intake is on the rear of the house, the side that just faces our big retaining wall, so adding an insulated external duct extension down the wall to a lower level where I can more easily get at it to clean it isn't going to be a problem at all. The plan originally was to just fit a large, coarse, washable, foam pre-filter on a new intake at a lower level, so I could easily just lift it out and wash it, with the hope that this pre-filter would help prevent the main pollen filter from getting clogged up so quickly. It was the hot weather this summer, combined with me looking at the best way to run the extended intake duct down the wall, that led to me noticing that it was fairly close to the ASHP. Running a couple of extra flow and return pipes, in parallel with those going through the wall to feed the UFH etc, would be easy, as would adding an extra cable through the existing ASHP cable duct with a control signal for a motorised valve. I already had a "cooling on" relay, with plenty of spare capacity to run another motorised valve, so I started thinking about modifying my new filter box to include a heat exchanger, motorised valve and a condensate drain tray. This all looks easy enough to do (I just need the time to do it). In practice, cooling the "wrong" side of the fresh air feed won't make any difference anyway, as any time that the cooling will be turned on the MVHR controller will have already moved the MVHR bypass valve to 100%, so the MVHR heat exchanger will be bypassed anyway, and the intake duct will be directly connected (via the filter) to the fresh air distribution ducts.

My problem is that I'm really a hardware person who happens to have had to do a bit of coding, so I approached monitoring our house from a hardware-driven perspective. I have several PICs all forming part of a wired network that gets real time from a GPS module, runs a RTC as a backup that's regularly updated by the GPS (every hour, which is total over-kill), collects data from a load of DS18B20's around the house, and outside, plus a couple of RH sensors and an NDIR CO2 sensor in the house and stores the data every 6 minutes to a USB stick, in .CSV text files that have file names in the format "month_year". Hanging off this is a four line LCD display in the hall that displays date, time (automatically corrected for BST), day of the week and some temperature, RH and CO2 data (handy to see how cold it is outside more than anything else, and for setting clocks around the house). All the data is transmitted slowly (2400 baud) over Cat6 cable, that's also used for power and connecting all the sensors. The whole lot is daisy chained, so one PIC acts as a data hub for all the sensors, sampling them as fast as it can (the limit's the DS18B20 12 bit conversion time) converting the sensor data into calibrated ASCII values, another two run the clock system (one for the RTC backup, one for the GPS) and transmits both time data and a "store a sample now" command every six minutes (starting on the hour), one just collates all the incoming date, time and measured data and sends a text line to the open file on the USB stick to store data on command. The model for adopting this distributed processing topology was my car, which uses loads of processors scattered around the car, with each dedicated to just an easily testable function. As someone who's not inherently at home writing loads of code, this method allowed me to develop each functional block and test it thoroughly on it's own, by just having a well defined I/O spec for that particular functional block. I won't pretend it's elegant, and it does suffer from the fact that it's not integrated into house LAN, but is entirely stand alone. This is a nuisance, as it means I have to turn it off to swap USB sticks over to get at the data. I like keeping the data on a USB stick, but one thing I want to do at some time is also send the data to the LAN, so I can have some form of simple web interface running on the RPi3 file server, perhaps, that allows me to pull off data at any time, without needing to go and get it off the USB stick. My problem is finding the time to be able to sit down and get to grips with doing this - I'm finding it harder to learn new stuff as I get older, and it takes me longer to pick things up than it used to. Whilst clearing junk from the old house out I came across a floppy disc and a fan fold paper print out of some Fortran 77 source code that I'd written back in the 1980s. It took me about half an hour to work out how the code worked, and it wasn't that complex, just a 3D trajectory prediction programme, that calculated an air launched weapon water entry point, with a known release point, height, airspeed, track, wind speed and direction and weapon ballistic data, and adding a correction for Coriolis effect. I remember re-writing that bit of code to run on a Psion, using OPL, at some point, so I must have been pretty familiar with it once, but I stared at it for ages before understanding how I'd done it all those years ago.

For clarification, trim heating with the MVHR would be fine. We don't use it as we don't seem to need it. Cooling is where the MVHR falls over, as we still seem to be able to get more than 1.5 kW of incidental heating plus solar gain in hot weather, and so the MVHR just can't draw heat out of the house fast enough on its own. Bearing in mind that we probably have around 300 W of background incidental heat gain (occupants, things that are running in the house etc) plus one or two kW of short period heat gain from cooking, it doesn't take much solar gain to start to cause the house to warm up. This Summer the MVHR would have been turned off at times, if it wasn't for the fact that it has an air-to-air heat pump that can cool down the fresh air delivered to the rooms, as with that heat pump off there were times when the MVHR would have been delivering air at over 30 deg C into the house, which would not have been welcome. I'm currently (well, not right now as I'm busy shifting junk around...) making a combined pre-filter and ASHP run pre-cooler for the MVHR intake, just to cool the incoling air when the MVHR is on 100% bypass in warm weather, and to save running the MVHR heat pump as well as the main ASHP. There should be an energy saving in doing this, as the additional demand on the ASHP should push it up into a slightly better operating region, so the incremental increase in energy that it will use should be less than the energy used by running the MVHR heat pump.

I can second @MikeSharp01s comments above. When planning our build I focussed very much on getting out of the ground, for two reasons; all the TV shows make the point repeatedly that that's where the greatest risk is in terms of unforeseen costs, and because we had a challenging plot that we already knew needed a heck of a lot of ground works (around £50k worth - and it's only a small plot). Fortunately all our ground works (with the exception of a long saga with our water borehole, which cost us a close to year in delays, but didn't end up costing us too much more money) went well. which lulled me into a bit of a false sense of security. Our frame went up quickly, with no snags, but it was around then that I realised that my large and, so I thought, comprehensive costing spreadsheet had missed out some items completely and seriously underestimated others (I underestimated the roofing cost, missed out things like skip and general site rubbish clearance cost, underestimated a lot of the internal fitting out costs and seriously underestimated the costs for landscaping and installing a SuDS compliant surface water drainage scheme). We ended up having to borrow another £50k over our planned budget, and even managed to blow that, hence the major slow down as I saved from my pension each month to buy materials to get work done on a piecemeal basis. Thankfully we will end up mortgage-free now our old house is almost sold, plus we'll be able to top our savings back up to pretty much the level they were at before we started the build. We've also just about ended up with a house that is worth a bit more than it cost us, but not by a lot. This latter point is one reason that I'm a bit sceptical of some of the TV shows that seem to show very cheap self-builds, without the owners having done a lot of the work themselves. I did a lot of work on our build, all the plumbing, kitchen fitting, most of the flooring, all the internal joinery (except hanging the doors), installing the ventilation system and heating and cooling systems, both bathrooms, the utility room and downstairs WC, and it still cost more than we'd budgeted for.

I can confirm that cooling using the MVHR isn't that effective; the volume of air moved just isn't great enough. A fan coil unit recirculates room air through the cooling coil and can have a much higher air flow rate, and hence much greater cooling effect. Our MVHR has a built in air-to-air heat pump, that can be used to deliver pretty cold air, but the maximum cooling power is only around 1.5 kW for the whole house, which isn't much on a day when there is a lot of solar gain. We've mitigated the solar gain as much as we can, both practically and in terms of what the planners would accept, but the greatest cooling influence on the whole house is just cooling the slab by reversing the ASHP and using the UFH as under floor cooling. That is far more effective than having the MVHR on full boost delivering cool air.

Guess who our supplier (and DNO) are? Both are SSE... As above, they make up the rules as they go along...

Spot on about the long thermal time constant of a house with a well-insulated concrete slab and high decrement delay insulation. Both @TerryE and I have found that the room temperature changes really slowly with changes in the outside air temperature. Left to it's own devices, with no heat input, the house settles at a temperature a few degrees above the mean diurnal temperature range over a few days, due to solar gain. We don't heat our slab at night (during the heating season) at all. In winter the slab gets heated once every couple of days for an hour or two normally, unless it's really cold, when we may have to heat the slab for and hour or so every day.

It's not set in stone, @Russdl, each supplier seems to have it's own rules. Some seem to make up rules as they go along....

That's right, you only get PD rights after a completion certificate has been issued, normally, or unless the planners consider that the house is complete (for the case where a completion certificate is delayed - essentially similar requirements to the point where the LA will want to start to charge you Council Tax).

EIC = Electrical Installation Certificate Our supplier wanted one for the consumer side installation before they would fit the meter.

The exhaust filter won't change the indoor air quality, but will make the MVHR run more efficiently, as there will be less flow resistance on the exhaust side, Measuring air quality is pretty complex, and hard to do properly. A simple particulate counter, that measures particulates in two dimensional bins (say, PM10 and PM2.5) doesn't really tell you much on it's own. You can be pretty certain that a well-fitted F7 intake filter will keep out most particulate allergens and harmful stuff from vehicle exhausts, combustion devices etc, but there are loads of harmless particulate sources inside the home, from all those tens of thousands of skin cells being shed all the time, through fragments of fibres from clothing and furnishings, to dust mites and particulates created when cooking food. The harmful small particulates tend to come from combustion, so vehicle exhaust, burning coal, wood and oil, etc. There are also gases emitted from combustion sources that are harmful, like nitrogen oxides etc, which you cannot filter out. Finally, any new house will take time for all the volatiles used in its construction to evaporate out of the structure. There are loads of these, from adhesives used in lots of materials, through to the paint used in the house, and they can take several months to evaporate away. The MVHR will help a great deal, by guaranteeing regular air changes, so the concentration of volatiles should drop steadily over the months, but it can be a slow process before the majority of the volatiles have evaporated off, plus there will always be new volatiles coming in, on everything from packaging to printed media.

You shouldn't be getting an particulate measurements (PMs) from drain smells, but you will get them from any dust particles in the air, so shed skin flakes, microscopic fibre fragments shed from clothes and soft furnishings, etc. Just counting the particulate concentration doesn't tell you much, unless you also have an idea as to what those particulates are. So, as an example, measuring particulates outside, near a road, means you'll have a pretty high likelihood of measuring vehicle-related PMs, which can be confirmed if you also measure something like NOx concentrations as well. Measuring particulate concentration in open countryside will most likely be measuring dust and pollen, plus things like spores. Measuring particulate concentration in a house where the intake filter is a well-fitted F7 (no point in having an F7 on the exhaust - change it for a G4, as all the F7 is doing is costing you more in additional resistance and electricity consumption through the MVHR, and reducing the MVHR efficiency) should mean that the particulate concentration will be mainly harmless stuff like skin flakes. We each shed around 30,000 to 40,000 skin cells per hour, and most of then end up in the air. A skin cell is around 25 to 40µ so will definitely register as a PM10!

Depends on the intake filter and how well sealed to the MVHR it is (we've seen some examples here where filters aren't that well sealed in some cases). A G4 filter will filter down to about 10µ, an F7 filter will filter down to about 1µ. So an F7 filter should remove all PM10s and a lot of PM2.5s (the numbers in the PM designation is the particle size in µ).

No, the sole plate was just nailed down to the concrete ring beam with those Timco fasteners. We can't put anything around the outside, as the "foundation" at frame level on the outside is just 200mm thick EPS, with the non-load bearing half of the Larsen-type truss bearing on it. Only the inner, load bearing half of the truss frame is secured to the 200mm x 200mm reinforced concrete ring beam that runs around the edge of the passive slab. With several tonnes of cellulose inside the frame I doubt it's going anywhere. Just checked, and each one of those fasteners is good for a 1.5 kN working tensile load, and at a guess there are over 100 of them holding our frame down (there's one in every 400mm wide bay, I think), so that's about 150 kN of hold-down force, or around 15 tonnes.

They didn't look like those Aussie ones. They were Irish, and our building inspector hadn't seen them before, so asked for one as a sample. I think they are these: http://www.timco.co.uk/fasteners-fixings/masonry-anchors/express-nails

Just to add that you're very far from being alone - going unexpectedly over-budget seems to be something that hits a lot of self-builders, even some of the most prepared. In our case we managed to afford to get the house built so it was secure, we weren't prepared to cut corners on what we wanted (this is planned to be our last ever home), so I ended up doing far more work myself than originally planned and we still ran out of money. I've spent the last two years only doing work when I've been able to save some money from my pension, so it's been very slow going, and that delay has cost us a lot of money in interest payments, council tax on two houses, etc. All I can say is that you will get over this, and with luck you will get the house you want. As a final point, I would like to add that I think that some of the TV shows about self-build have a lot to answer for, in that they often seem to play down the true cost, and make self-build look like a more affordable option than it often is. My personal view is that they rarely, if ever, give the true cost of most of the builds they show, and that may well mislead a lot of people.

I'm absolutely convinced, from personal experience and measurements, that SPF is a heck of a lot more accurate, as a measure of efficiency, than COP. The bottom line is that you can't fiddle SPF; it's the actual measured input energy over a year of an installed heat pump, operating in the UK climate, relative to the actual measure sensible heat that that unit has delivered over that period. COP is a short duration, standardised measurement at two different outside air and delivered water temperatures (for an ASHP) and takes no account of relative humidity, demand variation, defrost cycling etc, so will always be hopelessly optimistic.

As long as you adequately separate and insulate the 5V connections from the 230 VAC ones, then there's no problem - take a look at a typical ASHP connection strip as an example - you'll often find 12/24VDC dry contact connections as well as 230 VAC connections in reasonably close proximity. If it were me, then I'd try and make up some plastic shields to cover the 230 VAC connections just as belt and braces, but inside equipment it isn't required by the LV Directive to do this. I'd sense the pump using a flow switch in the pipe, as that's fail safe and provides isolation. A suitable one for low voltage use would be one of these: https://cpc.farnell.com/gentech-international/fs-02/flow-switch-300v-0-5amps/dp/SN35507 (Don't get the FS-01 as that uses an internal SSR, despite what the docs say about having a reed switch, so doesn't work at 5 VDC)